JPH025250B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring laser power, and more particularly to a method for measuring laser power using a fluid as a laser light absorbing load.

As laser technology has come to be applied to production processing machines and the like, the output of laser light has become dramatically higher, and measurement of the power of laser light has become increasingly important.

Conventionally, there is a laser power measurement method that measures the power of laser light from temperature changes using a solid load, but the power measurement of high-output laser light as described above depends on the heat resistance, durability, and reliability of the material. There are many difficulties, and no method has yet been developed that is sufficient to measure the power of high-power laser light.

The present invention has been made in view of the above points, and uses a fluid as a laser beam absorbing load, and allows the laser beam to be incident on the fluid load so that the energy of the laser beam is directly absorbed by the fluid load. It is an object of the present invention to provide a laser power measurement method that recovers latent heat into a fluid using a latent heat recovery device and measures the power of a laser beam from the temperature change of the fluid and the flow rate of the fluid.

The principle of this invention is to easily measure laser power by utilizing the property that the laser light of a carbon dioxide gas laser is well absorbed by water. That is, making laser light incident on water,
Some of this energy is absorbed by the water, and some of it becomes energy that increases the temperature of the water, and some of it becomes latent heat energy that evaporates the water and generates water vapor. As the energy of the laser beam increases and the power increases, the generation of latent heat also increases.
Measuring the rise in water temperature alone makes it impossible to accurately measure the power of the incident laser beam. In order to compensate for this point and measure electric power with high precision, latent heat energy is recovered as a rise in water temperature using a latent heat recovery device. The laser power of the laser beam can be measured by measuring the temperature rise of water due to energy and the flow rate. This invention will be explained below using the figures.

FIG. 1 is a three-dimensional perspective view showing the structure of a laser wattmeter which is an embodiment of the present invention. In the figure, reference numeral 1 denotes a cylindrical power meter main body, and the power meter main body 1 is provided with an introduction pipe 2 for introducing fluid H and a discharge pipe 3 for discharging the fluid H. 4 is a flow meter for measuring the flow rate of the fluid H, and is provided in the introduction pipe 2. 5 and 6 are temperature sensors for measuring the temperature of the fluid H; the temperature sensor 5 is provided in the introduction pipe 2 to measure the temperature before the laser beam is directed onto the fluid load; is provided in the discharge pipe 3 to measure the fluid velocity after irradiating the fluid load with a laser beam. 7 is a watering funnel for dropping the fluid H introduced into the power meter main body 1 in a shower style, 8 is a conical multilayer mesh, and 9 is the fluid H
This is a fluid load body shaping plate that guides the fluid to the irradiation position, and consists of a main body 9A shaped like a cap and a sub-body 9B similarly shaped like a cap provided at intervals above the main body 9A.The main body 9A has a hole in the upper center. A sub-body 9B is provided to cover this hole. Further, a gap 10 is partially formed between the main body 9A and the inner surface of the wattmeter main body 1, and the rest is sealed. 11 is a fluid load body shaped by the fluid load body shaping plate 9; 12 is the power meter main body 1
13 is a laser beam introduced from the laser beam introduction port 12. Reference numeral 14 represents a calibration heater, and reference numeral 15 represents a blower provided at the top of the power meter main body 1.

The blower 15, funnel 7, and multilayer mesh 8 constitute a latent heat recovery device.

Next, the operation of the laser wattmeter will be explained. The air pressure inside the power meter main body 1 is always maintained at a negative pressure below the atmospheric pressure by the blower 15 to prevent the evaporated fluid vapor from going out through the laser light inlet 12. The fluid H is guided into the introduction pipe 2 by a pump or the like, and falls through the flow meter 4.
The temperature of the fluid H whose flow rate has been measured by the flowmeter 4 is measured by the temperature sensor 5 before being irradiated with the laser beam 13, and is led to the latent heat recovery device and reaches the fluid load body shaping plate 9. This fluid load body shaping plate 9 absorbs the laser beam 13 so that the fluid H does not flow toward the laser beam introduction port 12 but guides it only to the opposite side, that is, to the irradiation position. When the laser beam 13 to be measured is introduced from the laser beam introduction port 12 while the fluid H is flowing down, the laser beam 13 is absorbed by the fluid H.
As the temperature of the fluid H increases, vapor of the fluid H is generated. This steam is sucked by the blower 15,
From the hole in the main body 9A of the fluid load body shaping plate 9 to the secondary body 9B
It rises through the bottom side of the body and is led to the latent heat recovery device. The steam led to the latent heat recovery device becomes a shower of water droplets smaller than the water funnel 7, and the steam is liquefied again by the multilayer mesh 8 and becomes part of the fluid H. At this time, latent heat is also absorbed by the fluid H, increasing the temperature of the fluid H. Then, the fluid H passes through the fluid load body shaping plate 9 and absorbs the laser beam 13 as a load, thereby increasing its temperature. The temperature of the fluid H whose temperature has increased in this manner is measured by the temperature sensor 6 through the calibration heater 14.

From the flow rate and temperature change of the fluid H obtained as described above, the laser power P of the laser beam can be measured using the following equation.

P (KW) = 4.18605÷60・A・ΔT・Q = 0.0697・A・ΔT・Q Where, A: Absorption coefficient ΔT of fluid load body: Temperature rise value of fluid [℃] Q: Fluid flow rate [/ min] For example, if the fluid flows at a rate of 1 per minute and the temperature rise of the fluid is 10°C, the laser power is calculated from the above equation.
It becomes 0.70AKW. Further, in the case of a carbon dioxide laser, water may be used as the laser light absorbing load, but in the case of other laser lights, the laser power can be measured by using mixed water containing a dye.

FIG. 2 is a diagram showing comparison data between the measurement of carbon dioxide laser power using the laser power meter according to the above embodiment and the measurement of laser power using the laser calorimeter method. The solid line in the figure shows the relationship between the laser calorimeter method and the power measurement according to the above embodiment, and the dotted line shows the case when the latent heat recovery device composed of the blower 15, watering funnel 7, and multilayer mesh 8 is stopped. show. As shown by the dotted line, it becomes impossible to measure the laser power from 3KW.

FIG. 3 is a diagram showing the results of a transient response speed test of the laser power meter according to the present invention. Figure a shows the falling characteristic, and Figure b shows the rising characteristic. Curve A
curve B shows the fluid load measurement method and curve B shows the laser calorimeter method. In the laser calorimeter method, the response time was approximately 20 seconds, but in the measurement method using a fluid load, an extremely fast response characteristic of 4.5 seconds can be obtained. There is no other high-output carbon dioxide laser power measuring instrument with such fast transient response characteristics.

In addition, in the above embodiment, the flow meter 4 is connected to the power meter main body 1.
However, since the flowmeter 4 is for measuring flow rate, it is natural that it may be installed at a location other than the introduction pipe 2.
Further, the fluid H may be something other than water.

As explained above, the laser power measurement method according to the present invention takes advantage of the property that fluid absorbs laser light, irradiates the fluid with laser light, and calculates the latent heat of the fluid vapor generated by the irradiation. Since the power of the laser light is measured from the fluid temperature before laser light irradiation, the fluid temperature after irradiation, and the flow rate of the fluid, the laser power of various lasers can be easily measured. In particular, it has an extremely excellent effect in that it is possible to measure high-power laser light.

[Brief explanation of drawings]

Fig. 1 is a three-dimensional perspective view showing the structure of a laser wattmeter that is an embodiment of the present invention, and Fig. 2 is data comparing the measurement results by the laser wattmeter shown in Fig. 1 and the measurement results by the laser calorimeter method. FIG. 3 is a diagram showing the transient response speed of the laser power meter shown in FIG. 1. In the figure, 1 is the power meter body, 2 is the introduction pipe, 3 is the discharge pipe, 4 is the flow meter, 5 and 6 are the temperature sensors,
7 is the playground. 8 is a multilayer mesh, 9 is a fluid load body shaping plate, 10 is a gap, 11 is a fluid load body, 12
13 is a laser beam introduction port, 13 is a laser beam, 14 is a calibration heater, and 15 is a blower.

Claims (1)

[Claims] 1 Using a liquid as a laser beam absorption load, irradiating this fluid with a laser beam, and recovering the latent heat of the fluid vapor generated by the laser beam irradiation into the fluid using a latent heat recovery device, to reduce the temperature of the fluid before the laser beam irradiation. A method for measuring laser power, comprising: measuring the power of a laser beam from the temperature of the liquid after irradiation and the flow rate of the fluid.